a) Field of the Invention
This invention relates to a cold water supply system for a multi-storey building, and also to methods of supplying cold water around such a building.
b) Description of the Prior Art
Traditionally, in many countries it has been the practice when furnishing a building with a cold water supply system to provide a relatively large capacity tank in the roof space of the building and to feed cold water to that tank from the mains supply through a pipe fitted with a ball valve sensing the water level in the tank. The various cold water faucets around the building are connected by suitable distribution pipes to the tank, except for one faucet nearest the point at which the cold water supply enters the building, which faucet is directly connected to the incoming mains water pipe and so operates at mains water pressure.
An advantage of the above system is that it is possible to use a relatively small diameter incoming mains water pipe, along which the flow rate is relatively restrictedxe2x80x94and which flow rate may well be lower than the maximum demand for example from a bath faucet. The pipe work connecting the tank to the faucets may be of a larger size than that of the incoming mains water pipe and so, for short periods, high flow rates may be achieved. Also, there is capacity in the event that the mains supply is interrupted.
A further advantage of the traditional cold water supply system described above is that the hot water system is also fed with cold water from the same cold water tank and so the water pressure available at the hot and cold faucets at one basin or bath is essentially the same.
A very significant problem with the traditional system described above is that the tank in the roof space rarely is serviced or cleaned out. The consequence is that various moulds, or other bacterial matter may contaminate the water in the tank, leading to a risk of disease. In many countries, regulations are being introduced for buildings to which the public has access, which regulations specify frequent emptying and cleansing of the tank, in order to reduce the likelihood of foreign organisms contaminating the cold water.
In the case of a multi-storey building, the mains water supply pressure may be insufficiently high to supply the upper storeys of the building. In such a case, it is usual to install a storage tank (usually referred to as a break tank) at the ground floor level and employ a local electrically-driven pump set to pump water either to a roof storage tank or directly to the faucets throughout the building, including on the upper storeys. The pump must be capable of meeting the instantaneous demand from the faucets in the building and so must have a relatively large maximum rate of pumping. As a consequence, the pump set arrangement must have a relatively high electrical power requirement. For example, a pump set for even quite small buildings may be rated at 5 hp or more.
An alternative cold water supply system, as widely used in Continental Europe, is to connect all of the cold water faucets in a building directly to the incoming mains supply pipe, and so wholly to obviate the use of a cold water storage tank. The disadvantage of this is that the flow rate available at any given faucet is limited to the maximum possible flow rate through the incoming supply pipe. In the event that more than one faucet is turned on, the maximum flow rate is divided between the opened faucets. As a consequence, the incoming mains water supply pipe usually must be of a significantly greater diameter to accommodate the maximum likely demand flow rate, as compared to a system employing a storage tank in the roof space of the building. This greatly increases the installation cost.
A further problem with a mains pressure supply system is that the hot water system must also operate at mains water pressure and this means special measures must be taken to accommodate the expansion of the water in the hot water system as the temperature of the water is raised, and so to prevent the pressure building excessively in the hot water system. Also, measures must be taken to prevent water being driven back down the incoming cold water supply pipe.
It will be appreciated that with a mains pressure cold water supply system as described above when fitted to a multi-storey building, the pressure available at faucets on upper floors will be less than the pressure available on lower floors. Thus, the pressure available at a bath (which usually has the highest flow rate demand in a domestic dwelling) may be unacceptably low, particularly if the bath is installed on the top floor of a building having more than two floors.
The present invention aims at addressing the problems associated with the supply of cold water to all of the floors of a multi-storey building, when employing a mains water pressure supply system without the use of a roof space storage tank.
Accordingly, one aspect of this invention, provides a cold water supply system for a multi-storey building having lower and upper floors and there being an external mains water supply for the building, which system comprises:
a water inlet pipe leading into the building from said external mains water supply;
a lower accumulator provided in the building on a lower floor thereof;
an inlet non-return valve arranged adjacent the lower accumulator and said inlet pipe being connected to the lower accumulator through said non-return valve;
an upper accumulator provided on an upper floor of the building;
a riser leading from the lower accumulator to the upper accumulator;
a lower non-return valve and an upper non-return valve disposed in said riser respectively adjacent the outlet from the lower accumulator and adjacent the inlet to the upper accumulator;
a water distribution pipe connected to the upper accumulator for supplying cold water to at least the upper floor of the building; and
an electrically-driven pump having a water inlet and a water outlet and arranged in the riser to pump water to the upper accumulator.
According to a second aspect of this invention, there is provided a method of supplying cold water to a multi-storey building having lower and upper floors, which method comprises:
supplying water through a water inlet pipe leading into the building from a mains water supply external of the building;
supplying the water from the inlet pipe though an inlet non-return valve to a lower accumulator provided in the building on a lower floor thereof, the inlet non-return valve being arranged adjacent the lower accumulator;
pumping water from the lower accumulator with an electrically-operated pump into a riser leading from the lower accumulator to an upper accumulator provided on an upper floor of the building, there being respective lower and upper non-return valves disposed in the riser adjacent the outlet from the lower accumulator and the inlet to the upper accumulator; and
supplying cold water from the upper accumulator to a water distribution pipe to distribute cold water to at least the upper floor of the building.
It is of course known to buffer pressure variations in water supply systems by using an accumulator. Though there are various designs of accumulator, a common type used in water supply systems has a pressure vessel with a resilient diaphragm dividing the vessel into two chambers. An inlet pipe communicates with one chamber and the other chamber is wholly sealed from both the first chamber and the atmosphere. The supply of water under pressure to said one chamber deforms the diaphragm and so compresses air in the other chamber. In this way, the accumulator may accept water or discharge water, dependent upon the relative pressures within the one chamber and in the pipe connected to that chamber, so smoothing variations in supply pressure.